JP2011054235A - Optical pickup device and optical disk device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device capable of stably obtaining high-quality recording or reproducing quality by reducing fluctuations in detection signals caused by stray light in a multilayered optical disk, and an optical disk device. <P>SOLUTION: Of the beams reflected by an optical disk, only peripheral beams excluding the push-pull region are used to generate a DPD signal in order to optimize internal wire connections among the light-receiving areas of the optical detector and thereby reduce the amplification factor of the lens error signal, required for generating the tracking error signal of the DPP method. A beam reflected from a multilayered optical disk is divided into some beam diffraction areas. The divided beam diffraction areas and the light-receiving areas are so arranged that the divided beams focus at different positions on the optical detector and that, when a beam is focused on a target layer, stray light from other than the target recording layer to be reproduced does not enter the servo signal light-receiving area of the optical detector. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical pickup device and an optical disk device.

  As background art in this technical field, for example, there is JP-A-2006-344344 (Patent Document 1). This publication describes that “a desired signal is accurately obtained from an optical disk having a plurality of recording layers”. Moreover, there exists Unexamined-Japanese-Patent No. 2006-344380 (patent document 2), for example. This publication describes that “a tracking error signal with a small offset is detected even when a recordable optical storage medium having two information recording surfaces is used”. Further, for example, Non-Patent Document 1 describes that “the tracking photodetector is arranged in an area free from other layers of stray light”, and the configuration thereof is also described in Japanese Patent Application Laid-Open No. 2004-281026 (Patent Document 3). .

  Moreover, there exists Unexamined-Japanese-Patent No. 2008-102998 (patent document 4), for example. This publication states that “when the target information recording layer of the optical disc is focused, the reflected light beam from the target information recording layer is focused on the light receiving portion of the photodetector, and information other than the target information recording layer is recorded. It is described that each region of the dividing element and the light receiving portion of the photodetector are configured so that the reflected light beam from the recording layer is not irradiated to the light receiving portion of the photodetector.

JP 2006-344344 A JP 2006-344380 A JP 2004-281026 A JP 2008-102998 A

IEICE Technical Report CPM 2005-149 (2005-10)

  In recent years, when recording or reproducing an optical disc having a multi-layered recording layer, stray light reflected by a recording layer that is not the target of reproduction is incident on the surface of the photodetector and becomes a disturbance component, which fluctuates the detection signal of the photodetector. There is a problem. In particular, in an optical disk having three or more recording layers, unnecessary light fluxes are generated in a plurality of layers, so that the disturbance component increases and the variation of the detection signal further increases. In order to solve the above-mentioned problem, Patent Document 4 provides a dividing element having a plurality of regions, and detects the light beam reflected by the optical disk by separating the stray light and the signal light by dividing the light beam into a plurality of light beams having different emission directions. Signal fluctuation is suppressed.

  However, in the above configuration, there is a signal that requires signal amplification of about 10 times for the signal used for the tracking error signal of the DPP system, and the signal fluctuation component due to the stray light that cannot be completely separated and remaining slightly, scratches, dirt, etc. There is a problem that the disturbance component of the signal is greatly amplified. As a result, the amplified disturbance component leaks into the DPP signal, and it is difficult to stably obtain high-quality recording or reproduction quality.

  The present invention provides an optical pickup device capable of generating a DPP signal while suppressing electrical signal amplification, greatly reducing leakage of a disturbance component into a detection signal, and stably obtaining high quality recording or reproduction quality. An object is to provide an optical disk device.

  The above object can be achieved by the invention described in the claims as an example.

  According to the present invention, it is possible to provide an optical pickup device and an optical disc device that can reduce the influence of disturbance due to stray light on a detection signal and can detect a high-quality signal.

Schematic which shows the structural example of the optical pick-up apparatus in this invention. Schematic which shows the light beam splitting element in a prior art example. Schematic which shows the structure of the photodetector in a prior art example. Schematic which shows the light beam splitting element in a 1st Example. Schematic which shows the structure of the photodetector in a 1st Example. Schematic which shows the structure of the photodetector in a 2nd Example. Schematic which shows the light beam splitting element in a 3rd Example. Schematic which shows the structure of the photodetector in a 3rd Example. Schematic which shows the structure of the photodetector in a 4th Example. Schematic which shows the structure of the photodetector in a 5th Example. 1 is a schematic diagram showing a configuration example of an optical disc apparatus according to the present invention.

  Hereinafter, details of embodiments of the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the component which shows the same effect | action.

FIG. 1 is a schematic configuration diagram showing an example of an optical pickup device according to a first embodiment of the present invention. The laser beam 2 emitted from the laser light source 1 has its path direction changed by the polarization beam splitter 3, the collimating lens 5 capable of correcting the spherical aberration of the incident beam by driving the stepping motor 4, and the polarization component orthogonal to each other at about 90 degrees. The light is condensed on a predetermined recording layer in the optical disk 8 by the objective lens 7 through a quarter-wave plate 6 that gives a phase difference.
The reflected light beam from the optical disk 8 passes through the objective lens 7 again, passes through the quarter-wave plate 6 and the polarizing beam splitter 3, and is split into a plurality of light beams by the light beam splitting element 10 and then enters the light detector 11. To do. The objective lens 7 is preferably mounted in an actuator 9 for driving in a predetermined direction. The actuator is driven to control the position of the objective lens. For the position control of the objective lens, tracking control using a tracking error signal and focus control using a focus error signal are executed. A liquid crystal element or the like may be used as the spherical aberration correction means.

  The above configuration is an optical system that is often used when recording or reproducing a multilayered optical disk. Therefore, first, specific configurations and problems of the conventional light beam splitting element and photodetector will be described. FIG. 2A shows an example of a schematic shape of the light beam splitting element 10 in the conventional example. The beam splitting element may be a diffraction grating, the diffraction grating surface may be divided into a plurality of regions, and a predetermined diffraction grating groove shape may be provided for each region. The beam splitting element is provided with a plurality of diffraction areas a and diffractive areas i. The reflected light beam reflected by the optical disc is diffracted by the track groove provided in the recording layer of the optical disc. Of the disc diffracted light, 0th-order disc diffracted light including the center of the light beam is incident on the diffraction region i, and 0th-order and + 1st-order disc diffracted light is incident on the diffraction regions a and b. Zero-order and −1st-order disc diffracted light is incident on the regions c and d. Further, a diffraction region e is adjacent to the diffraction region a, a diffraction region f is adjacent to the diffraction region b, a diffraction region g is adjacent to the diffraction region c, and a diffraction region is adjacent to the diffraction region d. h is provided. The light in the peripheral region of the 0th-order disc diffracted light beam is mainly incident on the diffraction region e and the diffractive region h. As long as it is within a range corresponding to the relationship between each incident light beam component and the diffraction region, the shape of each diffraction region may be changed, or the regions may be integrated or further divided. FIG. 2B shows a modification of the light beam splitting element as an example. The relationship between each diffraction region and the incident disc diffracted light maintains the above relationship.

  The light fluxes in the diffraction region a and the diffracting region d including the ± first-order disc diffracted light from the disc groove include a push-pull (hereinafter referred to as PP) signal component necessary for generating a tracking error signal. The relative positional relationship between the disk groove and the focused spot can be known from the PP signal. The light fluxes in the diffraction area e and the diffraction area h include a lens error signal component necessary for generating a tracking error signal. The lens error signal is a signal proportional to the amount of position movement of the objective lens mounted on the actuator.

  The + 1st order light and the −1st order light diffracted in each region are collected and incident on a plurality of light receiving surfaces provided in the photodetector 11 to detect signals. FIG. 3A is a schematic view showing a light receiving surface pattern and signal connection of the photodetector 11 of the conventional example. FIG. 3B shows a signal beam that is reflected light from a recording layer that is a target of recording or reproduction and a reflection from a layer that is not a target of recording or reproduction when recording or reproducing a multilayer optical disc. The light intensity distribution on the photodetector surface of light (hereinafter referred to as stray light) is shown. Of the light beams that have passed through the diffraction areas a, b, c, d, e, f, g, h, i, the + 1st order light is directed to the light receiving surfaces DET1, 4, 2, 3, 8, 6, 7, 5, 19 respectively. Incident light is formed to form condensing spots 45, 46, 47, 48, 49, 50, 51, 52, 61. The −1st order light beams that have passed through the diffraction regions e, f, g, and h are incident on the light receiving surfaces DET15, 17, 16, and 18, respectively, thereby forming condensing spots 57, 58, 59, and 60. The −1st-order light of the light beam that has passed through the diffraction regions a, b, c, and d is incident on the regions of the light receiving surfaces DET9 and DET14 for focus detection. However, since it is desirable to use the double knife edge method for detecting the focus error signal, no light is directly incident on DET 9 and DET 14 during focus control, and a light beam is incident between the respective light receiving surfaces so that the condensed spot 53 and the focused light are collected. A light spot 56 is formed. The tracking error signal is detected by a widely used differential push-pull method (hereinafter referred to as DPP method) and a differential phase detection method (hereinafter referred to as DPD method). The stray light reflected by the recording layer that is not symmetrically reproduced by the light beam dividing element is also divided into a plurality of light beams in the same manner as the signal light beam. Unlike the signal light spot, the stray light is out of focus with respect to the signal light collected on the surface of the photodetector, so that the stray light has a light intensity distribution which is not condensed and is blurred in a certain region. Of the stray light that has passed through the diffraction regions a, b, c, d, e, f, g, h, i, the + 1st order light forms spots 62, 63, 64, 65, 66, 67, 68, 69, 78. . The first-order light of stray light that has passed through the diffraction regions e, f, g, and h forms spots 74, 75, 76, and 77. The first-order light of stray light that has passed through the diffraction regions a, b, c, and d forms spots 70, 71, 72, and 73. As a result, the condensing spot from the diffraction region used for generating the tracking error signal can be configured so that no stray light is incident on the light receiving surface, and the detection signal can be prevented from fluctuating due to the stray light interfering with the signal light. It has become.

  Two or more light receiving surfaces for detecting the + 1st order diffracted light or the −1st order diffracted light in the diffractive region e and the diffractive region h are arranged in a substantially straight line in a direction substantially coincident with a direction corresponding to the radial direction of the optical disc. A configuration in which two or more light receiving surfaces for detecting the + 1st order diffracted light or the −1st order diffracted light in the diffraction grating region a and the leading diffraction region d are arranged in a direction substantially coincident with a direction corresponding to a tangential direction of the optical disc. Then, it can be set as the structure which is easy to avoid stray light at the time of an objective lens shift.

From the detection signal of the + 1st order light, the DPD signal and PP signal used as the information reproduction signal and tracking error signal are detected. The −1st order light is used to detect a focus error signal and a lens error signal. The DPP signal is generated by calculating a PP signal−k * lens error signal from the PP signal and the lens error signal. k represents the amplification factor by the amplifier.
Specifically, internal connection is performed as follows, and various signals are detected through signal calculation.
DET4 and DET6 are internally connected and the signal output through the current-voltage conversion amplifier 12 is A,
DET2 and DET7 are internally connected and the signal output through the current-voltage conversion amplifier 13 is represented by B,
DET3 and DET5 are internally connected, and a signal output through the current-voltage conversion amplifier 14 is represented by C,
DET1 and DET8 are internally connected and a signal output through the current-voltage conversion amplifier 15 is D,
DET15 and DET17 are internally connected, and the signal output through the current-voltage conversion amplifier 16 is L,
DET16 and DET18 are internally connected and the signal output through the current-voltage conversion amplifier 17 is represented by M,
The signal output from the DET 19 via the current-voltage conversion amplifier 18 is R,
DET10 and DET13 are internally connected and the signal output through the current-voltage conversion amplifier 19 is F1,
DET9, DET11, DET12, and DET14 are internally connected, and the signal output through the current-voltage conversion amplifier 20 is F2,
And An information reproduction signal and a servo control signal can be obtained from the output signal by the following calculation.
PP signal: (A + D)-(B + C)
Lens error signal: LM
DPP signal: PP signal−k * lens error signal ((A + D) − (B + C) −k * (LM))
Focus error signal: F1-F2
DPD signal: (A and B phase comparison) + (C and D phase comparison)
Information reproduction signal: A + B + C + D + R
In the conventional photodetector, a current-voltage conversion amplifier is not provided for each light-receiving surface to detect the signal, but the light-receiving surfaces are connected to each other inside the light detector, and then a current-voltage conversion amplifier is provided for the signal. By detecting, the number of current-voltage conversion amplifiers is reduced. This is to ensure the S / N necessary for detecting the information reproduction signal. As the number of current-voltage conversion amplifiers decreases, noise components can be reduced. Further, in the double knife edge method used for focus detection, the dark line region provided in the light receiving surface is deteriorated in the frequency characteristic of signal detection. Therefore, the signal from the light receiving surface should not be used for detection of the information reproduction signal. Therefore, the light quantity distribution of the + 1st order light and the −1st order light is set to about 4: 1, the + 1st order light is weighted, and the reproduction signal is detected only from the + 1st order light side where the light quantity is strong, and the current-voltage by the internal connection. Detection is performed with a configuration in which the number of conversion amplifiers is reduced. The focus error signal is detected with the first-order light having a weak light quantity. Therefore, the spectral ratio of the diffraction region of the light beam splitting element is set to about 0th order light: + 1st order light: -1st order light = 0: 4: 1, and blaze so that the light quantity of the + 1st order light is larger than the light quantity of the −1st order light. It is common to use a diffracted diffraction grating.

  In the following, problems of the conventional example will be described. The problem with the conventional example is that it is necessary to detect the lens error signal from the first-order light having a weak light quantity, and after the detection on the light receiving surface, the signal is electrically amplified by an amplifier with an amplification factor of about k = 10. It is necessary. In terms of geometric optics, the arrangement of the light receiving surface is such that stray light does not enter the light receiving surface in a multilayer disk. However, considering wave optics, it is difficult to completely separate stray light and signal light flux, and stray light is constant over a wide range. It will have a light quantity component. Accordingly, there is a slight stray light component incident on the light receiving surface. In particular, in multilayer optical discs where the layer spacing is narrow and there are multiple recording layers that cause stray light, the light quantity distribution of stray light on the surface of the photodetector becomes very complex, and it is very difficult to completely separate it from signal light. Become. Accordingly, the stray light is likely to enter the light receiving surface, and the stray light becomes a disturbance component and causes a change in the detection signal. The signal fluctuation due to the multilayer stray light is greatly amplified by the amplifier in the configuration of the conventional example and leaks into the DPP signal. In fact, with a conventional optical pickup, the lens error signal detected from the −1st order light is likely to vary in the multilayer optical disc. In addition to signal fluctuations due to multi-layer stray light, when disturbance components such as scratches and dirt leak into the lens error signal, they are greatly amplified by the amplifier, causing a serious deterioration in recording or reproduction quality. Thus, the conventional example has a problem that the lens error signal is very sensitive to various disturbances.

The lens shift signal component can also be detected from the light spot on the + 1st order light side of the diffraction region e and the diffraction region h. If it can be detected from here, there is no difference in the amount of light corresponding to the spectral ratio, and the amplification factor can be kept small. In addition, the light on the −1st order light side with a weak light quantity is easily affected by the manufacturing error of the diffraction grating, and there is a problem that the variation in the spectral ratio between the regions of the light beam splitting element becomes large. This becomes an offset factor of the DPP signal and lowers the recording or reproduction quality. Therefore, it is desirable to generate the DPP signal using only the light of the + 1st order light on the side where the light amount is strong from the viewpoint of variation in spectral ratio. However, for the DPD signal detection, four signals are detected: the sum signal of the diffraction areas a and e, the sum signal of the diffraction areas b and f, the sum signal of the diffraction areas c and g, and the sum signal of the diffraction areas d and h. There is a need. Therefore, when all the signals necessary for PP and DPD signal generation are detected independently through the current-voltage conversion amplifier without being connected and are generated by calculation, there are 9 current-voltage conversion amplifiers used for detecting the information reproduction signal. The S / N is greatly deteriorated. In order to avoid this, the internal connection reduces the number of current-voltage conversion amplifiers to five to achieve both detection of the PP signal, the DPD signal, and the information reproduction signal with less noise. In the above configuration, a signal on the + 1st order light side of the lens shift signal to be subtracted from the PP signal when the DPP signal is calculated is added to the PP signal. Accordingly, the lens error signal cannot be detected from the + 1st order light, and the conventional example has a configuration in which the lens error signal must be obtained from the −1st order light having a small light amount.
As a result of adding the light quantity difference of the spectral ratio and the lens shift signal component of the + 1st order light to PP, the amplification factor becomes a very large value of about k = 10.

  As described above, since the configuration of the conventional example detects the DPD signal and reduces the number of current-voltage conversion amplifiers for securing the S / N, the lens error necessary for generating the DPP signal is reduced. The electrical amplification factor of the signal has become a large value of about k = 10. Therefore, in the present invention, by introducing a new DPD signal detection method, the amplification factor of the amplifier necessary for generating the DPP signal is greatly suppressed to about 1 to 2 and various signals equivalent to the conventional ones are obtained. An optical pickup device to be used. As a result, it is possible to provide an optical pickup device that is resistant to disturbances such as multilayer stray light, diffraction grating spectral ratio variations, scratches, and the like, has a good yield, and stably obtains high quality recording / reproducing quality.

  First, a new DPD signal detection method according to the present invention will be described. In the conventional DPD method, DPD signal detection is performed using substantially the entire area of the signal beam as described above. In the present invention, attention is paid to the peripheral region of the signal light beam excluding the PP signal region of the signal light beam. That is, it was examined whether the DPD signal can be detected only with the light flux in the peripheral area of the light flux corresponding to the diffraction area e and the diffractive area h. As a result of the examination, it has been found that a DPD signal of good quality can be detected only with the luminous flux in the peripheral region. The DPD signal does not detect the change in the amount of light itself as a signal, but detects the timing difference (phase difference) at which the amount of light changes, and uses the amount of change in the phase difference as a signal. This is because even if the area is reduced, a signal can be generated as long as the timing of light quantity change can be detected. According to the novel DPD detection method of the present invention, the peripheral areas of the light receiving surfaces DET1 and 8 and DET2, 7DET3, 5DET4, and 6 that have been forced to reduce the current-voltage conversion amplifier in the conventional example are not required. It has been found that the DPD signal can be detected only by the signals DET5, 6, 7, and 8 on which the luminous flux in the region enters. By using the DET5, 6, 7, and 8 signals, the lens error signal can be generated on the + 1st order light side with a strong light intensity and the DPD signal can be detected by eliminating the need for the internal connection by the novel DPD detection method of the present invention. is there. Therefore, the amplification factor of the amplifier can be greatly reduced. Specifically, the amplification factor can be greatly reduced to about 1.5.

  Hereinafter, a specific configuration of the present invention will be described. FIG. 4 is a schematic view showing a configuration of the light beam splitting element 10 in the present invention. Although within the range of the above-described modification of the conventional example, the diffraction regions b and c are integrated with the diffraction regions a and d, respectively. The diffraction regions e, f, g, and h are preferably set to the same spectral ratio as in the conventional example. The diffraction areas a and d may have the same spectral ratio as in the conventional example, or a spectral ratio in which the light amount is concentrated only on the + 1st order light. The diffraction region i may have the same spectral ratio as in the conventional example. FIG. 5 is a schematic view showing a light receiving surface configuration and a connection method in the present invention.

Of the light beams that have passed through the diffraction regions a, d, e, f, g, h, and i, the + 1st order light is incident on the DETs 1 ′, 2 ′, 3 ′, 5 ′, 4 ′, 6 ′, and 15 ′, respectively. Of the light beams that have passed through the diffraction regions e, f, g, and h, the −1st order light is incident on the regions of the light receiving surfaces DET7 ′ and DET14 ′ for focus detection. However, since it is desirable to use the double knife edge method for detecting the focus error signal, the signal light beam does not directly enter DET7 ′ and DET14 ′ during the focus control, and the light beam enters between the light receiving surfaces.
Each signal is obtained by the following calculation.
A signal output from the DET 5 ′ via the current-voltage conversion amplifier 21 is represented by A ′,
A signal output from the DET 4 ′ through the current-voltage conversion amplifier 22 is represented by B ′,
A signal output from the DET 6 ′ through the current-voltage conversion amplifier 23 is represented by C ′,
A signal output from the DET 3 ′ through the current-voltage conversion amplifier 24 is represented by D ′,
A signal output from the DET 1 ′ through the current-voltage conversion amplifier 25 is represented by L ′,
A signal output from the DET 2 ′ through the current-voltage conversion amplifier 26 is represented by M ′,
The signal output from the DET 15 ′ via the current-voltage conversion amplifier 27 is R ′,
DET8 ′ and DET14 ′ are internally connected, and the signal output through the current-voltage conversion amplifier 28 is F1 ′,
DET10 ′ and DET12 ′ are internally connected, and the signal output through the current-voltage conversion amplifier 29 is F2 ′,
DET9 ′ and DET11 ′ are internally connected, and the signal output through the current-voltage conversion amplifier 30 is F3 ′,
DET7 ′ and DET13 ′ are internally connected, and the signal output through the current-voltage conversion amplifier 31 is F4 ′,
And An information reproduction signal and a servo control signal can be obtained from the output signal by the following calculation.
PP signal: L'-M '
Lens error signal: (A ′ + D ′) − (B ′ + C ′)
DPP signal: PP signal−k * lens error signal (L′−M′−k * {(A ′ + D ′) − (B ′ + C ′)})
Focus error signal: (F1 ′ + F3 ′) − (F2 ′ + F4 ′)
DPD signal: (A 'and B' phase comparison) + (C 'and D' phase comparison)
Information reproduction signal: A ′ + B ′ + C ′ + D ′ + L ′ + M ′ + R ′
The number of current-voltage conversion amplifiers is seven, which is an increase from the five in the conventional example. However, if there are two, the amount of deterioration is not large, and the performance of the current-voltage conversion amplifier itself is improved. It is a level that can be improved by optimizing sensitivity settings. In addition, since the number of spots on the surface of the photodetector is reduced, it is possible to easily adjust the photodetector and improve the yield by taking the PP region from one diffraction region and the corresponding light receiving surface. is there.

  The light beam splitting element 10 in the round trip path may be disposed between the polarization beam splitter 3 and the quarter wavelength plate 6. Since the distance between the photodetector and the beam splitting element is extended, there is an advantage that the required diffraction grating pitch can be increased and the element can be easily manufactured. In addition, since the effective diameter of the light beam on the diffraction grating surface also increases, the degree of deterioration of various signals with respect to the positional deviation of the element becomes moderate. However, in order not to cause the light beam splitting element to act on the outward light beam, it is desirable that the diffraction grating of the light beam splitting device is a polarization diffraction grating having polarization properties so that it acts only on the return light beam.

  It is desirable to arrange the light receiving surfaces in accordance with the basic configuration of the conventional example so that the stray light can be easily avoided. Accordingly, the two or more light receiving surfaces for detecting the + 1st order diffracted light or the −1st order diffracted light in the diffraction region e and the diffractive region h are substantially straight in a direction substantially coincident with the direction corresponding to the radial direction of the optical disc. The two or more light receiving surfaces for detecting the + 1st order diffracted light or the −1st order diffracted light in the diffraction grating region a and the diffractive region d are arranged in a direction substantially coincident with the direction corresponding to the tangential direction of the optical disc. It is good to have a line-up configuration. Therefore, the arrangement of the light receiving surfaces is not limited to the arrangement shown in FIG. If the correspondence between the light flux from each diffraction region and the incident light receiving surface does not change, the arrangement position of each light receiving surface may be changed. Accordingly, the light beam may be incident on the corresponding light receiving surface by matching the diffraction direction and angle of the light beam splitting element. The light receiving surface group detected by the focus error signal does not detect the information reproduction signal or other control signals. Therefore, not only the position of the light receiving surface pattern but also the addition of a new light receiving surface and internal connection Modifications such as changing the output signal and adding a current-voltage conversion amplifier may be freely made.

  With the above configuration, the PP signal and the lens error signal can be detected on the + primary light side where the light intensity is strong, and the DPD signal can be detected, and the lens error signal can be detected from the + primary light side having the same spectral ratio as the PP signal. As a result, the amplification factor of the amplifier can be greatly reduced, and the amplification factor is about 1.5. Therefore, an optical pickup device that is resistant to various disturbance fluctuations such as interference fluctuation due to multi-layer stray light and scratches and dirt on the optical disk and can suppress signal deterioration due to variation in spectral ratio, and can stably obtain high quality recording / reproducing quality is provided. can do.

  A second embodiment will be described with reference to FIG. In this embodiment, by using a light beam splitting element that is easier to manufacture than in the first embodiment, it is possible to suppress variations in mass production of the light beam splitting element and stabilize the performance of the single element of the optical pickup device. Yield improvement and cost reduction can be achieved.

  The optical system configuration of the optical pickup device in the present embodiment may be the same as that of the optical pickup device shown in FIG. The difference from the first embodiment is the configuration of the light beam splitting element 10 and the photodetector 11. Therefore, the configuration of the photodetector 11 which is the main part of the second embodiment will be described with reference to FIG.

  In the optical system configuration of the first embodiment, the diffraction grating pitch of the diffraction region i is likely to be the smallest. If the pitch of the diffraction grating is reduced, the diffraction efficiency is likely to change due to the influence of manufacturing errors. As a result, performance variation of the optical pickup occurs, resulting in a decrease in yield. Therefore, only the diffraction area i is provided with a rectangular grating in which the light amounts of the + 1st order light and the −1st order light are equal. Compared to the blazed grating used in the first embodiment, the rectangular grating is very easy to manufacture and can greatly suppress variation in performance. The shape of each diffraction region may be the same as in the first embodiment.

  FIG. 6 shows a schematic diagram of a photodetector when the diffraction region i is a rectangular grating. The difference from the first embodiment is the light receiving surface configuration for receiving the light beam from the diffraction region i and its internal connection. Since the diffraction region i is a rectangular grating and the light amount is evenly allocated to the ± first-order light, the light amount of the + 1st-order light is reduced compared to the first embodiment. Therefore, a new DET 16 ′ is also provided to detect −1st order light in the diffraction region i in which the amount of light is increased. Further, the DET 15 'and the DET 16' may be internally connected and output as the signal R 'without increasing the current-voltage conversion amplifier.

The correspondence between the other diffraction regions and the light receiving surface, the internal connection, and the signal calculation method may be the same as those in the first embodiment. Specifically, of the light beams that have passed through the diffraction regions a, d, e, f, g, and h, the + 1st order light is incident on the DETs 1 ′, 2 ′, 3 ′, 5 ′, 4 ′, and 6 ′, respectively. Of the light beams that have passed through the diffraction regions e, f, g, and h, the −1st order light is incident on the regions of the light receiving surfaces DET7 ′ and DET14 ′ for focus detection. However, since it is desirable to use the double knife edge method for detecting the focus error signal, the signal light beam does not directly enter DET 7 'and DET 14', but the light beam enters between the respective light receiving surfaces. The tracking error signal performs signal detection using the DPP method and the DPD method which are widely used in general. In the diffraction region i provided with the rectangular diffraction grating grooves, the + 1st order light is incident on the light receiving surface DET15 ′ and the −1st order light is incident on the light receiving surface DET16 ′.
Each signal is obtained by the following calculation.
A signal output from the DET 5 ′ via the current-voltage conversion amplifier 21 is represented by A ′,
A signal output from the DET 4 ′ through the current-voltage conversion amplifier 22 is represented by B ′,
A signal output from the DET 6 ′ through the current-voltage conversion amplifier 23 is represented by C ′,
A signal output from the DET 3 ′ through the current-voltage conversion amplifier 24 is represented by D ′,
A signal output from the DET 1 ′ through the current-voltage conversion amplifier 25 is represented by L ′,
A signal output from the DET 2 ′ through the current-voltage conversion amplifier 26 is represented by M ′,
DET15 ′ and DET16 ′ are internally connected, and the signal output through the current-voltage conversion amplifier 27 is R ′,
DET8 ′ and DET14 ′ are internally connected, and the signal output through the current-voltage conversion amplifier 28 is F1 ′,
DET10 ′ and DET12 ′ are internally connected, and the signal output through the current-voltage conversion amplifier 29 is F2 ′,
DET9 ′ and DET11 ′ are internally connected, and the signal output through the current-voltage conversion amplifier 30 is F3 ′,
DET7 ′ and DET13 ′ are internally connected, and the signal output through the current-voltage conversion amplifier 31 is F4 ′,
And An information reproduction signal and a servo control signal can be obtained from the output signal by the following calculation.
PP signal: L'-M '
Lens error signal: (A ′ + D ′) − (B ′ + C ′)
DPP signal: PP signal−k * lens error signal (L′−M′−k * {(A ′ + D ′) − (B ′ + C ′)})
Focus error signal: (F1 ′ + F3 ′) − (F2 ′ + F4 ′)
DPD signal: (A 'and B' phase comparison) + (C 'and D' phase comparison)
Information reproduction signal: A ′ + B ′ + C ′ + D ′ + L ′ + M ′ + R ′
That is, in this embodiment, by using a light beam splitting element that is easier to manufacture than in the first embodiment, the mass production of the light beam splitting element is suppressed, the performance of the single element is stabilized, and the yield of the optical pickup device is improved. Improvement and cost reduction can be achieved, and the amplification factor of the amplifier can be greatly reduced to about 1.5. Thus, there is an advantage that it is possible to provide an optical pickup device that is resistant to disturbances such as multi-layer stray light interference and can stably obtain a high quality recording / reproducing signal with less performance variation during mass production than the first embodiment.

  Next, a third embodiment will be described with reference to FIGS. In this embodiment, an optical pickup device capable of detecting a high-quality information reproduction signal with fewer noise components by reducing the number of current-voltage conversion amplifiers used for information reproduction signal detection than in the first embodiment is provided. To do.

  The optical system configuration of the optical pickup device in the present embodiment may be the same as that of the optical pickup device shown in FIG. The difference from the first embodiment is the configuration of the light beam splitting element 10 and the photodetector 11. Therefore, the configurations of the light beam splitting element 10 and the photodetector 11 which are the main parts of the third embodiment are shown in FIGS. 7 and 8, respectively.

The configuration of the light beam splitting element may be the same as that of the conventional light beam splitting element described in the first embodiment. The diffraction regions a, b, c, d, e, f, g, h, and i are preferably set to the same spectral ratio as in the conventional example.
The PP signal is detected from the + 1st order light in the diffraction region a and the diffractive region d, the lens error signal is detected from the + 1st order light in the diffraction region e and the diffractive region h, and the −1st order light in the diffraction region e and the diffractive region h is detected. The DPD signal is detected, a focus error signal is detected from the −1st order light in the diffraction region a and the diffraction region d, and an information reproduction signal is detected from the + 1st order light in the diffraction region a and the diffraction region i. A feature of the second embodiment is that a new DPD signal that uses the region around the light beam is detected from the side of the −1st-order light having a low light quantity. As described above, the DPD signal detects the signal change timing, and obtains the tracking error signal from the phase difference amount of the change timing. Therefore, there is an advantage that an accurate tracking error signal can be obtained as long as the signal change timing can be detected even if the signal light amount is weak, and the light amount change is more resistant to disturbance than the DPP signal that directly becomes the tracking error signal. Therefore, the DPD signal detected from the light beam peripheral portion is detected from the first-order light having a weak light quantity. As a result, only the PP signal and the lens shift signal need be obtained from the + 1st order light side, so that the light receiving surfaces DET1 and 4, the light receiving surfaces 2 and 3, the light receiving surfaces 5 and 7, and the light receiving surfaces 6 and 8 are internally connected. Thus, the number of current-voltage conversion amplifiers can be reduced to five, which is the same as the conventional example. Since the lens error signal is detected from the + 1st order light, the amplification factor of the lens error signal can be reduced to about k = 1.5, which is equivalent to the first embodiment.

  FIG. 8 is a schematic view showing the configuration of the photodetector 11 in the present invention. Of the luminous fluxes that have passed through the diffraction regions a, b, c, d, e, f, g, h, i, the + 1st order light is incident on DET1, 4, 2, 3, 8, 6, 7, 5, 19 respectively. Of the light beams that have passed through the diffraction regions e, f, g, and h, the −1st order light is incident on the DETs 15, 17, 16, and 18, respectively. The −1st-order light of the light beam that has passed through the diffraction regions a, b, c, and d is incident on the regions of the light receiving surfaces DET9 and DET14 for focus detection. However, since it is desirable to use the double knife edge method for detecting the focus error signal, no light is directly incident on DET9 to DET14, but a light beam is incident between the respective light receiving surfaces.

Each signal is obtained by the following calculation.
A signal output from the DET 17 via the current-voltage conversion amplifier 32 is A ′,
A signal output from the DET 16 via the current-voltage conversion amplifier 33 is represented by B ′,
A signal output from the DET 18 via the current-voltage conversion amplifier 34 is represented by C ′,
A signal output from the DET 15 via the current-voltage conversion amplifier 35 is represented by D ′,
DET1 and DET4 are internally connected, and the output signal of the current-voltage conversion amplifier 36 is L ′,
DET2 and DET3 are internally connected, and the output signal of the current-voltage conversion amplifier 37 is M ′,
DET6 and DET8 are internally connected, and the output signal of the current-voltage conversion amplifier 38 is P ′,
DET5 and DET7 are internally connected, and the output signal of the current-voltage conversion amplifier 39 is Q ′,
A signal output from the DET 19 via the current-voltage conversion amplifier 40 is represented by R ′,
DET10 and DET13 are internally connected, and the signal output through the current-voltage conversion amplifier 41 is F1 ′,
DET9, DET11, DET12, and DET14 are internally connected, and the signal output through the current-voltage conversion amplifier 42 is F2 ′,
And An information reproduction signal and a servo control signal can be obtained from the output signal by the following calculation.
PP signal: L'-M '
Lens error signal: P'-Q '
DPP signal: PP signal−k * lens error signal (L′−M′−k * (P′−Q ′))
Focus error signal: F1'-F2 '
DPD signal: (A 'and B' phase comparison) + (C 'and D' phase comparison)
Information reproduction signal: L ′ + M ′ + P ′ + Q ′ + R ′
As described above, since the DPD signal detected at the periphery of the light beam is detected from the first-order light having a low light amount, the light receiving surfaces DET1 and 4, the light receiving surfaces 2 and 3, the light receiving surfaces 5 and 7, and the light receiving surfaces 6 and 8 are provided. Each can be internally connected to output a signal, and the number of current-voltage conversion amplifiers can be reduced to five, which is the same as in the conventional example.

  That is, in this embodiment, the number of current-voltage conversion amplifiers used is reduced by adopting a configuration in which the DPD signal detected in the peripheral portion of the light beam is detected from the first-order light having a low light amount, which is lower than that in the first embodiment. There is an advantage that a high-quality information reproduction signal with less noise can be obtained. In addition, the amplification factor of the amplifier can be greatly reduced to about k = 1.5, and an optical pickup device that can stably and high-quality record / reproduce signals that are resistant to disturbances such as multilayer stray light interference can be provided.

  A fourth embodiment will be described with reference to FIG. In this embodiment, by using a light beam splitting element that is easier to manufacture than in the third embodiment, the mass production of the light beam splitting element is suppressed, the performance of the single element is stabilized, and the yield of the optical pickup device is improved. Improvement and cost reduction can be achieved.

  The optical system configuration of the optical pickup device in the present embodiment may be the same as that of the optical pickup device shown in FIG. The difference from the first embodiment is the configuration of the light beam splitting element 10 and the photodetector 11. Therefore, the configuration of the photodetector 11 which is the main part of the fourth embodiment will be described with reference to FIG.

  In the optical system configuration of the first embodiment, the diffraction grating pitch of the diffraction region i is likely to be the smallest. If the pitch of the diffraction grating is reduced, the diffraction efficiency is likely to change due to the influence of manufacturing errors. As a result, performance variation of the optical pickup occurs, resulting in a decrease in yield.

  Therefore, only the diffraction area i is provided with a rectangular grating in which the light amounts of the + 1st order light and the −1st order light are equal. Compared to the blazed grating used in the first embodiment, the rectangular grating is very easy to manufacture and can greatly suppress variation in performance. The shape of each diffraction region may be the same as in the first embodiment.

  FIG. 9 is a schematic view showing an example of the configuration of a photodetector when the diffraction region i is a rectangular grating. The difference from the third embodiment is the configuration of the light receiving surface that receives the light beam from the diffraction region i. Since the diffraction region i is a rectangular grating and the light amount is evenly allocated to the ± first-order light, the light amount of the + 1st-order light is reduced compared to the first embodiment. Therefore, a new DET 20 is provided to detect the −1st order light beam from the diffraction region i. Further, DET19 and DET20 may be internally connected and output as signal R ', and there is no increase in the current-voltage conversion amplifier.

  The correspondence between the other diffraction regions and the light receiving surface, the internal connection, and the signal calculation method may be the same as those in the first embodiment. Specifically, of the light beams that have passed through the diffraction regions a, b, c, d, e, f, g, and h, the + 1st order light is incident on the DETs 1, 4, 2, 3, 8, 6, 7, and 5, respectively. The first-order light among the light beams that have passed through the diffraction regions e, f, g, and h are incident on the DETs 15, 17, 16, and 18, respectively. The −1st-order light of the light beam that has passed through the diffraction regions a, b, c, and d is incident on the regions of the light receiving surfaces DET9 and DET14 for focus detection. However, since it is desirable to use the double knife edge method for detecting the focus error signal, no light is directly incident on DET9 to DET14, but a light beam is incident between the respective light receiving surfaces. The tracking error signal performs signal detection using the DPP method and the DPD method which are widely used in general. In the diffraction region i provided with the rectangular diffraction grating grooves, the + 1st order light is incident on the light receiving surface DET19 and the −1st order light is incident on the light receiving surface DET20.

Each signal is obtained by the following calculation.
A signal output from the DET 17 via the current-voltage conversion amplifier 32 is A ′,
A signal output from the DET 16 via the current-voltage conversion amplifier 33 is represented by B ′,
A signal output from the DET 18 via the current-voltage conversion amplifier 34 is represented by C ′,
A signal output from the DET 15 via the current-voltage conversion amplifier 35 is represented by D ′,
DET1 and DET4 are internally connected, and the output signal of the current-voltage conversion amplifier 36 is L ′,
DET2 and DET3 are internally connected, and the output signal of the current-voltage conversion amplifier 37 is M ′,
DET6 and DET8 are internally connected, and the output signal of the current-voltage conversion amplifier 38 is P ′,
DET5 and DET7 are internally connected, and the output signal of the current-voltage conversion amplifier 39 is Q ′,
DET19 and DET20 are internally connected, and the output signal of the current-voltage conversion amplifier 40 is R ′,
DET10 and DET13 are internally connected, and the signal output through the current-voltage conversion amplifier 41 is F1 ′,
DET9, DET11, DET12, and DET14 are internally connected, and the signal output through the current-voltage conversion amplifier 42 is F2 ′,
And An information reproduction signal and a servo control signal can be obtained from the output signal by the following calculation.
PP signal: L'-M '
Lens error signal: P'-Q '
DPP signal: PP signal−k * lens error signal (L′−M′−k * (P′−Q ′))
Focus error signal: F1'-F2 '
DPD signal: (A 'and B' phase comparison) + (C 'and D' phase comparison)
Information reproduction signal: L ′ + M ′ + P ′ + Q ′ + R ′
That is, in this embodiment, by using a light beam splitting element that is easier to manufacture than in the third embodiment, the mass production of the light beam splitting element is suppressed, the performance of the single element is stabilized, and the yield of the optical pickup device is increased. Improvement and cost reduction can be achieved, and the amplification factor of the amplifier can be greatly reduced to about 1.5. Accordingly, there is an advantage that it is possible to provide an optical pickup device that is resistant to disturbances such as multi-layer stray light interference and stably obtains a high quality recording / reproducing signal with little variation in performance during mass production.

  Next, a fifth embodiment will be described with reference to FIG. The present embodiment provides an optical pickup device that can reduce the number of current-voltage conversion amplifiers used for information reproduction signal detection and obtain a high-quality information reproduction signal with fewer noise components than the first embodiment. .

The optical system configuration of the optical pickup apparatus in this embodiment may be the same as that of the optical pickup apparatus of the first embodiment shown in FIG. The difference from the first embodiment is the configuration of the photodetector 11. FIG. 10 shows a photodetector 11 which is a main part of the fifth embodiment. The DPD signal is a tracking error signal detection method based on a ROM disk. This is because the DPD signal detects the phase difference of the change in the amount of light, but this change in the amount of light is caused by the recording pit provided on the ROM disk. However, for example, in a Blu-ray disc (hereinafter referred to as BD), the ROM disc also supports the DPP method, so that it is not always necessary to detect the DPD signal. Therefore, the optical pickup apparatus of this embodiment does not detect the DPD signal itself, but the ROM disk also detects the DPP tracking error signal, thereby further increasing the internal connection of the light receiving surface and increasing the number of current-voltage conversion amplifiers. It aims to reduce the noise component of the information reproduction signal. The beam splitting element may be the same as in the first and second embodiments. Further, the arrangement of the light receiving surface of the photodetector may be the same as that in the first and second embodiments. The difference from the first and second embodiments is the internal connection method from the light receiving surfaces DET3 ′ to DET6 ′ to the current-voltage conversion amplifier 43 and the current-voltage conversion amplifier 44. FIG. 10 shows an example of the light receiving surface pattern when the diffraction region i is a rectangular diffraction grating groove.
DET3 ′ and DET5 ′ are internally connected, and a signal output through the current-voltage conversion amplifier 43 is P ′,
A signal output through the current-voltage conversion amplifier 44 by internally connecting DET4 ′ and DET6 ′ is Q ′. Thus, a lens error signal is generated by P′−Q ′, and an information reproduction signal is generated by L ′ + M ′ + P ′ + Q ′ + R ′. Other internal connection methods and signal calculation methods may be the same as those in the first and second embodiments.

  With the above configuration, the number of current-voltage conversion amplifiers affecting the information reproduction signal can be reduced from seven to five. That is, this embodiment has an advantage that a high-quality information reproduction signal with less noise than that of the first embodiment can be obtained.

  FIG. 11 is a schematic diagram of an optical disk device on which the optical pickup device according to the first to fifth embodiments is mounted. 8 is an optical disk, 910 is a laser lighting circuit, 920 is an optical pickup device, 930 is a spindle motor, 940 is a spindle motor drive circuit, 950 is an access control circuit, 960 is an actuator drive circuit, 970 is a servo signal generation circuit, and 980 is information A signal reproduction circuit, 990 is an information signal recording circuit, and 900 is a control circuit. The control circuit 900, the servo signal generation circuit 970, and the actuator drive circuit 960 control the actuator in accordance with the output from the optical pick pickup 920. By using the output from the optical pickup device in the present invention for actuator control, stable and highly accurate information recording and information reproduction can be performed.

  Further, the optical pickup device using the present invention is not limited to the optical system as shown in FIG. 1, the optical system configuration described in the embodiment, or the light receiving surface configuration.

  By using each of the above-described means, it is possible to obtain good reproduction quality when recording or reproducing a multilayered optical disc.

  The embodiments of the optical pickup device according to the present invention and the optical disk device using the same have been described above. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications are made without departing from the scope of the present invention. be able to. That is, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 ... Laser light source, 2 ... Laser beam, 3 ... Polarizing beam splitter, 4 ... Stepping motor, 5 ... Collimating lens, 6 ... 1/4 wavelength plate, 7 ... Objective lens, 8 ... Optical disk, 9 ... Actuator, 10 ... Light beam Splitting element 11... Photo detector 18 to 44 Current-voltage conversion amplifier 910... Laser lighting circuit 920... Optical pick-up device 930 Spindle motor 940 Spindle motor drive circuit 950 Access control circuit 960 ... Actuator drive circuit, 970 ... Servo signal generation circuit, 980 ... Information signal reproduction circuit, 990 ... Information signal recording circuit, 900 ... Control circuit

Claims (16)

A laser light source;
An objective lens for condensing the laser beam emitted from the laser light source onto the optical disc;
A light beam splitting element that splits the signal light beam reflected by the optical disc into a plurality of light beams;
An optical pickup device comprising a photodetector having a plurality of light receiving surfaces for receiving the signal light beams divided into a plurality of parts,
Of the signal light beam divided by the light beam splitting element, the light detector detects the light in the peripheral region of the light beam excluding the push-pull signal region,
An optical pickup device that detects a DPD signal serving as a tracking error signal by using a detection signal from light in the periphery of the light beam. The optical pickup device according to claim 1,
The beam splitting element has at least seven diffraction regions;
Of the disc diffracted light diffracted by the track grooves provided in the recording layer of the optical disc,
Zero-order disc diffracted light including the center of the light beam is incident on the first diffraction region,
The 0th-order and + 1st-order disc diffracted light is incident on the second diffraction region,
The third diffraction region is incident with 0th and −1st order disc diffracted light,
The fourth and fifth diffraction regions adjacent to the second diffraction region are incident on the light beam peripheral region of the zero-order disc diffracted light,
The light in the peripheral region of the light flux of the 0th-order disc diffracted light is incident on the sixth and seventh diffraction regions adjacent to the third diffraction region,
The fourth and sixth diffraction regions are adjacent to each other;
An optical pickup device characterized in that the fifth and seventh diffraction regions are also adjacent to each other. The optical pickup device according to claim 1,
The light beam splitting element is a diffraction grating, and the diffraction grating surface is divided into a plurality of regions, each having a predetermined diffraction grating groove shape,
An optical pickup device characterized in that the diffraction grating of the light beam splitting element is blazed so that the light amount ratio of + 1st order diffracted light and -1st order diffracted light is different. The optical pickup device according to claim 1,
The light beam splitting element is a diffraction grating, and the diffraction grating surface is divided into a plurality of regions, each having a predetermined diffraction grating groove shape,
The diffraction grating of the light beam splitting element has a diffraction grating region blazed so that the light amount ratio of the + 1st order diffracted light and the light amount of the −1st order diffracted light are different from each other;
An optical pickup device, wherein a light quantity of + 1st order diffracted light and a rectangular diffraction grating region where light quantities of -1st order diffracted light are equal are mixed. The optical pickup device according to claim 3,
A PP signal is detected from the primary light of the sign on the side where the light intensity of the second and third diffraction regions is strong among the light beams divided by the light beam splitting element,
A lens error signal proportional to the amount of movement of the objective lens and the DPD signal are detected from the primary light of the sign on the side where the light intensity of the fourth to seventh diffraction areas is strong,
A focus error signal is detected from the primary light of the code on the side where the light intensity of the fourth to seventh diffraction regions is weak,
An optical pickup apparatus for detecting an information reproduction signal from primary light having a sign with a higher light quantity in first to seventh diffraction regions. The optical pickup device according to claim 3,
A PP signal is detected from the primary light of the sign on the side where the light intensity of the second and third diffraction regions is strong among the light beams divided by the light beam splitting element,
A lens error signal is detected from the primary light of the sign on the side where the light intensity of the fourth to seventh diffraction regions is strong,
The DPD signal is detected from the primary light of the sign on the side where the light intensity of the fourth to seventh diffraction regions is weak,
A focus error signal is detected from the primary light of the sign on the side where the light intensity of the second and third diffraction regions is weak,
An optical pickup apparatus for detecting an information reproduction signal from primary light having a sign with a higher light quantity in first to seventh diffraction regions. The optical pickup device according to claim 4,
A PP signal is detected from the primary light of the sign on the side where the light intensity of the second and third diffraction regions is strong among the light beams divided by the light beam splitting element,
The lens error signal and the DPD signal are detected from the primary light of the sign on the side where the light intensity of the fourth to seventh diffraction regions is strong,
A focus error signal is detected from the primary light of the code on the side where the light intensity of the fourth to seventh diffraction regions is weak,
An optical pickup apparatus for detecting an information reproduction signal from primary light having a sign on the side where the light intensity in the second to seventh diffraction regions is strong and ± first-order light in the first diffraction region. The optical pickup device according to claim 4,
A PP signal is detected from the primary light of the sign on the side where the light intensity of the second and third diffraction regions is strong among the light beams divided by the light beam splitting element,
A lens error signal is detected from the primary light of the sign on the side where the light intensity of the fourth to seventh diffraction regions is strong,
The DPD signal is detected from the primary light of the sign on the side where the light intensity of the fourth to seventh diffraction regions is weak,
A focus error signal is detected from the primary light of the sign on the side where the light intensity of the second and third diffraction regions is weak,
An optical pickup device that detects an information reproduction signal from primary light with a sign on the side where the light intensity is strong in the first to seventh diffraction regions and ± primary light in the first diffraction region. The optical pickup device according to claim 1,
Two or more light receiving surfaces for detecting + 1st order diffracted light or −1st order diffracted light in the fourth to seventh diffraction grating regions are arranged in a substantially straight line in a direction substantially corresponding to a direction corresponding to a radial direction of the optical disc;
Two or more light receiving surfaces for detecting the second and third diffraction grating regions + 1st order grating diffracted light or −1st order grating diffracted light are arranged in a direction substantially coincident with a direction corresponding to a tangential direction of the optical disc,
When the light beams from the first to seventh diffraction regions are focused on the target recording layer of the optical disc, the reflected light beam from the target recording layer is reflected on the light receiving surface of the photodetector. Each of the light beams from the second to seventh diffraction regions is configured such that the reflected light beam from the recording / reproducing layer other than the target information recording layer is not irradiated onto the light receiving surface of the photodetector. An optical pickup device characterized by that. The optical pickup device according to claim 1,
An optical pickup device characterized in that a signal amplification factor of the lens error signal necessary for generating a DPP signal using a tracking error signal is in a range of 1 to 2. A laser light source;
An objective lens for condensing the laser beam emitted from the laser light source onto the optical disc;
A light beam splitting element that splits the signal light beam reflected by the optical disc into a plurality of light beams;
An optical pickup device including a photodetector having a plurality of light receiving surfaces for receiving light beams divided into a plurality of light beams by the light beam dividing element,
An optical pickup device that detects only a DPP signal as a tracking error signal. The optical pickup device according to claim 11,
The beam splitting element has at least seven diffraction regions;
Of the disc diffracted light diffracted by the track grooves provided in the recording layer of the optical disc,
Zero-order disc diffracted light including the center of the light beam is incident on the first diffraction region,
The 0th-order and + 1st-order disc diffracted light is incident on the second diffraction region,
The third diffraction region is incident with 0th and −1st order disc diffracted light,
The fourth and fifth diffraction regions adjacent to the second diffraction region are incident on the light beam peripheral region of the zero-order disc diffracted light,
The light in the peripheral region of the light flux of the 0th-order disc diffracted light is incident on the sixth and seventh diffraction regions adjacent to the third diffraction region,
The fourth and sixth diffraction regions are adjacent to each other;
An optical pickup device characterized in that the fifth and seventh diffraction regions are also adjacent to each other. The optical pickup device according to claim 11,
A PP signal is detected from the primary light of the sign on the side where the light intensity of the second and third diffraction regions is strong among the light beams divided by the light beam splitting element,
A lens error signal is detected from the primary light of the sign on the side where the light intensity of the fourth to seventh diffraction regions is strong,
A focus error signal is detected from the primary light of the code on the side where the light intensity of the fourth to seventh diffraction regions is weak,
An optical pickup apparatus for detecting an information reproduction signal from primary light having a sign on the side where the light intensity in the second to seventh diffraction regions is strong and ± first-order light in the first diffraction region.   Claims 1 to 13 having a function of reproducing each information signal recorded on a plurality of recording layers provided at predetermined intervals in the optical disc and a function of recording each information signal on each recording layer. The optical pickup device described.   15. An optical pickup device according to claim 1, a laser lighting circuit for driving the laser light source in the optical pickup device, and a signal detected from the photodetector in the optical pickup device. An optical disc apparatus equipped with a servo signal generation circuit for generating a focus error signal and a tracking error signal and an information signal reproduction circuit for reproducing an information signal recorded on the optical disc.   16. The optical disc apparatus according to claim 15, comprising a function of reproducing each information signal recorded on a plurality of recording layers provided at predetermined intervals in the optical disc, and a function of recording each information signal on each recording layer. .

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